Blade sharpener



FIG. 1 is a first perspective view of a new and ornamental design for a blade sharpener;

FIG. 2 is a front elevation view thereof;

FIG. 3 is a rear elevation view thereof;

FIG. 4 is a first side elevation view thereof;

FIG. 5 is a second side elevation view thereof;

FIG. 6 is top plan view thereof; and,

FIG. 7 is a bottom plan view thereof.

The broken lines depict portions of the blade sharpener in which the design is embodied that are not considered part of the claimed design. 

CLAIM The ornamental design for a blade sharpener, as shown and described. 